Calibration is a task for determining the relationship between the output values of a measuring apparatus, a measuring device, values represented by a material measure or a reference material and the associated values, which are defined by standards, of a measurement variable under predefined conditions.
DE 199 37 203 A1 provides for the calibration of a measuring bearing during mounting. Specifically, the intention is for a sensor system made up of strain gages gauges to determine load components of the bearing on the basis of stresses resulting from rolling contact. The aim is to calibrate the bearing as realistically as possible. Therefore, provision is also made for the bearing to be calibrated with a preload during mounting.
In order to determine the reference values, a comparison installation/reference installation with defined individual influencing variables is provided. The influencing variables on the bearing, which are to be measured, are for example:                the overlap in press fits resulting from diameter differences in the bearing seat,        temperatures,        stresses resulting from loads,        stresses resulting from Hertzian stress during rolling contact,        vibrations,        dimensional deviations within the permissible production tolerances.        
Influencing variables of this type are always superimposed with disturbance variables during real individual mounting. Disturbance variables are, for example, also those which are also to be assigned to the group of the above-mentioned influencing variables. During calibration, these disturbance variables have a disadvantageous effect on the result of the calibration operation, that is to say also on the measured values, since they may corrupt the measurement result.
Measured values are variables which result from the influences, such as stresses resulting from overlaps. The reference values provided in relation to the measured values are standard values which are determined on the basis of a representative group of individual values. The reference values have the same physical unit as the specific measured values.
Although a preload is applied in the method according to DE 199 203 A1, the bearing is rotated in a defined manner in the installation and therefore, during adjustment, the inherent weight of the structure to be mounted is taken into account relatively accurately, however, for example the influence of the press fits resulting from the bearing seat is not included in the reference value.
An installation also has further disturbance variables which cannot be reproduced on a comparison installation or can be reproduced only with a great deal of outlay. These are, in particular, influences from the surrounding structure (device) which are subject to fluctuations in terms of behavior and structure. Influences of this type are, for example, fluctuations in the thickness of the material or defects in the material. Influences of this type can, for example, strongly influence the vibration behavior or the transmission of vibrations. Further disturbing influences are vibrations from assembly devices and other production devices in the vicinity of the bearing to be calibrated. Under certain circumstances, the influences severely corrupt the results. This can lead to incorrect assessment of measurement results.
Calibrating each individual bearing in the installation is relatively complicated and, as already mentioned, is susceptible to disturbing influences. To some extent, calibration is possible only with great difficulty or is not possible at all on account of the inability to access the mounted bearing. Vehicle manufacturers therefore often refrain from using measuring bearings, for example in vehicle transmissions.